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[smerby]

Hi All

 

Between 1910-1940 there was an accelerated global surface warming of ~.5 C as CO2 emissions increased around 5-10 ppm. Between 1975 and 2005, surface temps rose ~.6 C with a much larger CO2 increase of nearly 50 ppm. How could similar jumps in temperature result from such different increases in CO2 emissions. 

 

Thanks for for help

 

Smerby

[nflwxman]

Hi All

Between 1910-1940 there was an accelerated global surface warming of ~.5 C as CO2 emissions increased around 5-10 ppm. Between 1975 and 2005, surface temps rose ~.6 C with a much larger CO2 increase of nearly 50 ppm. How could similar jumps in temperature result from such different increases in CO2 emissions.

Thanks for for help

Smerby

There are quite a few papers on the early 20th century warming. I would check AGWobserver, they have a section devoted to early 20th century warming. My basic takeaway from reading through many of the main studies is that a mix of anthropogenic GHGs (not just CO2), large increase in solar activity, and black carbon albedo darkening of the arctic ice sheets are the main contributors. Secondary contributors are ocean oscillations like the PDO/ENSO which trended positive in the timeline you outlined. The difference between then and the last 40 years or so, is that there is no natural oscillation or product that explain a large portion of the late 20th century warming period (this will probably spark a debate, but that is the mainstream thinking). The early 20th century warming was driven primarily by the high latitudes, and not nearly as spatially diverse as the current period. I would check out some of those abstracts on agw observer and come to your own conclusions.

[skierinvermont]

Hi All

 

Between 1910-1940 there was an accelerated global surface warming of ~.5 C as CO2 emissions increased around 5-10 ppm. Between 1975 and 2005, surface temps rose ~.6 C with a much larger CO2 increase of nearly 50 ppm. How could similar jumps in temperature result from such different increases in CO2 emissions. 

 

Thanks for for help

 

Smerby

 

Because other things effect temperature besides CO2. This does not negate the fact that CO2 is a greenhouse gas and that for every doubling of CO2, there is a surface forcing of 3.7W/m2, which causes the earth to warm 1.2C. Including the subsequent net feedbacks, total warming is predicted to be 1.5-4.5C per doubling (net feedbacks are very likely somewhere between weakly and strongly positive).

[smerby]

Thanks Guys

[Mohansingh]

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[Snow_Miser]

We really don't know why the early-20th Century Warming rate was about the same as the late-20th Century warming trend. In the models, the change in net forcing was totally different during each warming phase, yet, a similar amount of warming and rate of warming occurred. This means that the current radiative forcings in the models cannot explain the early-20th Century warming. 

 

This suggests to me a larger solar forcing, or a stronger source of internal variability.